Thermohydraulic Analysis of Aqueous Dispersions Effectiveness with TiO2 and Al2O3 Nanoparticles in a U-Shaped Geothermal Probe

The paper deals with the influence of Al2O3 and TiO2 nanoparticle admixtures to the water coolant on the heat exchange and the pumping power of its single-phase flow in the U-shaped vertical collector of the heat pump geothermal probe. The heat carrier is aqueous dispersions with TiO2 and Al2O3 nanoparticles at volume concentrations of 0.1 %, 0.3 %, 0.6 %, 1.0 % and 1.3 %. Studies were performed for turbulent single-phase flow with a range of Reynolds numbers 11,500–67,000 and Euler numbers 48–75 and compared with similar results for a water coolant. The optimal volume fraction of nanoparticles in the coolant, at which nanofluids provide the lowest pumping capacity of the coolant compared to the base fluid, ensuring the required heat transfer coefficient at the level of 2230 W∙m-2∙K-1 is analyzed in the article.